1. Field of Invention
The present invention relates to an electrostatic capacitance detection device, which reads surface contours of an object having a fine indentation, such as a fingerprint, by detecting an electrostatic capacitance, which changes according to the distance from the surface of the object.
2. Description of Related Art
Conventionally, an electrostatic capacitance detection device used for fingerprint sensor or the like is formed of a sensor electrode and a dielectric layer, provided on the sensor electrode, on a single crystal silicon substrate. See, for example, Japanese laid-open patent publication No. 11-118415, No. 12-346608, No. 13-56204 and No. 13-133213). FIG. 1 shows an operating principle of the conventional electrostatic capacitance detection device. A sensor electrode and a dielectric layer form an electrode and a dielectric layer of a capacitor, and a human body becomes the other electrode, which is grounded. The electrostatic capacitance CF of this capacitor changes depending on the indentation of a fingerprint contacting the surface of the dielectric layer. A capacitor having the electrostatic capacitance Cs is prepared on the semiconductor substrate, and the two capacitors are coupled in series and a predetermined voltage is applied thereon. This allows an electric charge Q to be generated between the two capacitors depending on the indentation of the fingerprint. The electric charge Q can be detected using a usual semiconductor technology, and surface contours of the object can be read.